1. Field of the Art
The present invention relates to 4(1H)-quinolone derivatives. These compounds generally act on cardiac muscle to increase its contractility, and some of these compounds increase selectively the cardiac muscle contractility without causing the extensive increase of heart rate. That is to say they have a cardiotonic effect.
2. Related Art
Cardiovascular diseases such as congestive heart failure, angina pectoris, nephredema or hepatic edema tend to increase with the advancement of age.
The factors for supporting the function of heart, are heart rate, preload, postload, cardiac muscle contracting force and the like. As the cause of congestive heart failure, all of the abnormalities of the aforementioned factors are significant, among which decrease of the cardiac muscle contractility is critical.
As a drug for increasing the contractility of the cardiac muscle, digitalis has traditionally been used. However, the range of the pharmaceutically active amount and the toxicity of digitalis is narrow, and digitalis tends to cause intoxication so that it is difficult to administer as a drug for enhancing the cardiac muscle contractility. Therefore, a strong cardiotonic agent having higher safety is desired as a substitute for digitalis.
In these years, as the remedies of heart failure, there have been developed salmazol derivatives, bipyridine derivatives, imidazolone derivatives and the like. However, most of these drugs are known to increase heart rate together with the increase of the contractility and thus to increase the oxygen consumption of the heart muscle, so that the failure of the heart muscle is often stimulated adversely.